Wave transmission system



Nov. 7, 1933. RL. DAVIS WAVE TRANSMISSION SYSTEM Filed Nov. 7, 1927 mm0% :5; Q

INVENTOR Babe/7 L. D0 W5.

I ATTORNEY Patented Nov. 7, 1933 UNITED STATES V WAVE TRANSMISSIONSYSTEM Robert L.'Davis, Pittsburgh, Pet, assignor to West-- inghouseElectric & Manufacturing corporation of Pennsylvania C any, an

Application November 7, 192,71 Serial N01: 231,52I

' '1 Claims. .(Cl. 250-27) My invention relates broadly towave-transmission systems and it has particular relation to. safetydevices used, therein for preventing abnormal circuit conditionsfromcausing damage.

Within the past few years, thepower output of radio transmission systemshas steadily increased. It is not at all uncommon, at the present time,to radiate, in the form of high-frequency oscillatory energy, as much as50 to. 100 kilowatts from a single station. tor, and oscillator tubesemployed in high-power stations all handle large amounts of power andare easily damaged by. excessive overloads. Such tubes are relativelyexpensive, and it is highly desirable that they shall be protectedagainst,

damage by a plurality of safety devices. In the patent to Ryan,1,565,505, means are shown whereby a plurality of abnormal conditionsare each instrumental in causing, the removal of power from thethermionic devices. Among such conditions may be mentioned (1) decreasein the flow of, cooling water, (2) too high temperature of thecooling'water, (3) overloading of the poweramplifier tubes, (4) ab- 7normal current in the power transformer and, (5) exposure of energizedapparatusto accidental contact by the'operator. Insofar as I am aware,however, previous workers in the art have not fully appreciated thenecessity of providing means for preventing the application of platepotential to power tubes in the event that the grids thereof are notbiased to the proper negative potential, and have overlooked thepossibilities of tube-damage caused by the resulting heavy platecurrent. e

It is accordingly an object of my inventionto provide, in wavetransmission systems of the type comprising high-power tubes,instrumentalities that function to prevent the application of plate;potential to such tubes in the event that the grids thereof are notproperly biased. It is a further object of my invention to provide, insystems of the type referred to, instrumentalities which will functionto deprive any given tube ofhplate potential in the event of failure ofthe grid-bias-potential supply thereto. .gAnothr objectof my inventionis to provide instrumentalities.whereby-each ofa plurality ofpower-tubes connected in cascade shall be supplied with plate potentialin proper sequence, upon theactuation of a single control-device.Another'and more specific objectof my invention is to provide, in wavetransmission systems of; the type'in which are utilized a master oscil-The amplifier, modulae.

lator and a plurality of power amplifiers, instrumentalities which willfunction to deprive the power amplifiers of plate potential in the eventthat the grid-bias-potential supply to the master oscillator isinterrupted.

In one commercial. embodiment of my invention, I attain the abovereferred-to objects by interposing relay devices in thecondiictorssunplying grid-bias potential to each of the powertubes, andinterpose additional relay devices in the plate circuits ofthe'individual tubes, so arranging the second-mentioned relay devicesthat they are controlled by the first-mentioned relaydevices. 7

Among the novel features of my'invention are those particularly setforth in the appended invention.

The apparatus illustrated inthe drawing comprises a thermionicoscillator 1 coupled in cascade to a thermionic amplifier 2,.which,'inturn,

-is coupled-to a second thermionic amplifier 3,

preferably of higher power.

Each of the thermionic devices comprises a filament 4, a-Vgrid Sand 2.plate. 6, and is supplied with filamentpower from a source 7, whichsource may be either a battery or a generaton as shown.

The plateor output circuit of the thermionic oscillator may beconsidered as comprising two distinctportions, (l) a tuned loopconsisting of an'inductor 8, shunted by a tuning condenser 10, in whichloop flows the high-frequency component of the plate current and, (2) adirect-cure rent path comprising a radio-frequency choke 1 1,-

1 the fixed contactlZ and movable armature. 13. of .a relay 14, a source15 of high potential and a conductor 16 connecting thenegative pole ofthe source 15 to the filament. The oscillation gen-j orator is notprovidedwith a distinct and separate input circuit, grid excitationtherefor being obtained through a condenser. 1'7 whichcouples thegrid 5to the oscillatory output circuit.

with an output circuit comprising an inductor 18 shunted by a tuningcondenser 20, andhighpo- .tential for the plateof the device is suppliedfrom l The thermionic amplifierdevice 2 is provided 7 a generator 21through a circuit which includes the movable armature 22 and fixedcontact 23 of a relay 24, and a radio-frequency choke coil 25. The gridof the thermionic amplifier 2 is coupled to the output circuit of thepreceding oscillator through a condenser 26.

The second thermionic amplifier 3 is provided with an output or tankcircuit comprising an inductor 2'7 shunted by a tuning condenser 28,

and plate potential for the amplifier is supplied,

from a generator 30 over a circuit which includes a movable armature 31and fixed contact 320i a relay 33, and'a radio-frequency choke coil- 34.

The output circuit 27-28 is coupled, by means of a variable reactor 35,to a radiation structure which preferably includes an antenna 36, avariable inductor 3'7 and a ground connection 38, or 21;

counterpoise.

The winding of the relay 14, associated with the high-potential supplycircuit forv the thermionic.

oscillator 1, is arranged to beenergized from a battery 40, theenergizing circuit comprising a conductor 45, a conductor 41 and thefixed contact 42 and movable armature 43 of a relay 44.

The winding of the relay 24, associated'with the plate-potential supplyfor the first amplifier tube 2, is supplied with current from thebattery 40 over a circuit including the conductor 45, a conductor 4-6,the movable armature 4'7 and the fixed contact 48 of a relay 50 and aconductor 51' which is connected to the conductor 41.

, The winding of the relay 33, associated with the plate-potentialsupply circuit of the second amplifier device 3, is supplied withcurrent from the battery 40 over a circuit including the conductor 45,21conductor 52, the'fixed contact 53 and the movablearmature 54'of arelay55 and the conductor 51.

In order tosupply grid-biasing potential for the several thermionicdevices, I provide a generator 56 havinga resistor 57 and the winding ofthe relay 44 connected in shunt thereto. The generator 56is preferablyactuated by a driving motor 58 which is supplied with power from any 45convenient commercial source, the supply circuit including the fixedcontact 59 and the movable contact 60 of a relay 61.

The filaments of the thermionic devices 1, 2 and 3 are. connected to thepositive end of the resistor 5'7, adjacent to the relay 44, through aconductor 62, thus maintaining the filaments at a positive potentialwith respect to all points onthe resistor aslong as current is passingthrough the resistor from the generator 56,. -The grid of the thermionicoscillator l is con-,

nected to a point on the resistor 56 near the positive end thereof, bymeans of a conductor 63, the connection including a radio-frequencychoke coil 64. The grid of the first amplifier device is connected to amore negative point on the resistor 5'? by means of a conductor 65, theconnection including aradio-frequency choke coil 66 and the windingofthe relay 50. The grid of the sec ond thermionic amplifier isconnected'to a still 21, 30 and 56 maybe replaced by storage batfthebias-potential generator 56.

teries, if desired, or suitable rectifiers may be substituted therefor.

In order to explain the operation of a wavetransmission system arrangedaccording to my invention, it should first be assumed that potential hasbeen supplied to the motors driving the generators 15, 21, 30 and '7.The starting switch 70 is then closed, completing the filament supplycircuit for the thermionic devices, and energizing the winding of therelay 61. As soon as the relay 61 is energized, the armature 60 is drawnagainst the fixed contact 59, closing the circuit which suppliespotential to the motor 58 which drives A current then fiows intheresistor 57, in the direction indicated by the arrow, and through thewinding of the relay 44, causing the armature 43 thereof to be attractedtoward, and make contact with, the fixed contact 42. A circuitisaccordingly completed through the conductors 45 and 41 which permits thebattery 40 to energize the winding of the relay 7 14 associated with theplate potential supply circuit of the oscillator device '1. Upon-enegization of the relay 14*, the armature 13 "is drawn against the fixedcontact 12 ,and plate-potential is accordingly applied to theoscillator1, permitting the generation of oscillations thereby.

'As soon oscillatory currents appear in the outputcircuit of theoscillator tube, theyare ap pliedacross the input circuit of the firstampliier tube through the coupling'condenser 26 and the conductor 62.During positive halfcycles, electrons are attracted tothe grid of theampli fier tube, and a grid current accordingly flows through a circuitwhich may betraced fromthe' 1 10 grid through the choke coil 66, thewinding of the relay 50, the resistor 57 and over the conductor 62 whichis connected to the filaments of all of the tubes. The relay 50, beingaccordingly energized, pulls up the armature 47 and completes a circuitwhich permits the application of potential from the battery 44 to thewinding of the relay 24 associated with the plate supply circuit oi thefirst amplifier tube.

Theenergizing circuit for the relay 24 may be 1 traced from the positivepole of the battery -40 over the conductor 45, through the winding ofthe relay, the movable contact 47 of the relay 50, the fixed contact 48of the same relay-,the conductor 51, the fixed contact'42 of the relay44, the armature 43 of the same relay and back tothe negative pole'ofthe battery. The armature 22 of the relay 24 is accordingly caused tomove against the fixed contact 23 associated therewith, and potential isapplied from the generator 21 to 1 the plate of the amplifier tube.

The oscillations generated by-the oscillationgenerator tube willaccordingly be amplified and repeated in the output circuit of theamplifier tube, which circuit comprises theinductor 18 and 1 the tuningcondenser 20. A portion of the potential drop across the output inductoris applied to the input circuit of the second amplifier tube 3 by meansof a coupling condenser 71 and the conductor 62; 7 i The sequence ofoperations :above described'i n connection with the application o'fplate pote'n tialto the first amplifier tube is now repeated inconnection with asecond amplifier tube; The relay 55 beingenergizedbythe rectifiedgrid our 1 rent in the amplifier tube-3,"permitsthe energi zation of the relay 33 to apply potential to the plate of thesecond amplifiertube. As soon as plate potential is applied, inthemanner'just described, the tube begins to function as an amplil fier,and the resulting oscillations in the output circuit thereof may besupplied to the radiating structure by means of a coupling device of anyappropriate type.

After the system has reached a stable state, the connections of theseveral grids to the resistor may be so readjusted, if desirable,that'each the1= mionic device receives the proper grid-biasingpotential. Obviously, if the points of connection of the conductors 63,and 67 are moved toward the negative end of the resistor, the biaspotentials on the respective grids will become more negative withrespect to the common filament connection 62, and vice versa.

If, for any reason, the bias potential generator 56 fails, the relay 44will be deenergized, and

holding current will be removed from the relays 14, 24 and 33 associatedwith the high-potential supply circuits for the several tubes. Shouldthe oscillator tube cease to function, input excitation for the'firstamplifier stage would also cease and, consequently, the relay 50 wouldbe deenergized by reason of the cessation of grid current through thewinding thereof. The deenergization of this relay would in turndeenergize the relay 24 associated with the plate supply circuit for thefirst amplifier tube and that tube would cease delivering inputexcitation to the second amplifier tube. Inasmuch as the relay 55 would,accordingly, be deprived of holding current, the relay 33 associatedwith the high-potential supply circuit of the second amplifier tubewould be .deenergized, permitting the said circuit to'be broken;

If, for any reason, the grid-leak circuit of I either the oscillatortube or the first amplifier tube thrown abruptly on the system, but isapplied gradually, inasmuch as the several tubes go progressively intooperation.

Although I have shown the relays 14, 24 and 33 as connected in circuitbetween the high-potential generators 15, 21. and 30 and theindividualthermionic devices supplied with plate potential thereby, these relaysmay quite advantageously be inserted in'the circuits which supplypotential to the motors driving the several generators. The switch '70may also be included in the circuit supplying energy to the motor (notshown) which drives the generator 7, in which event the entiretransmission system can be set into operation in proper sequence by themere closing of the said switch. I

In addition, my invention prevents the application of plate potential toany tube which is not properly biased, and a destructive plate currenttherein is accordingly obviated.

limited except insofar as is necessitated by the In addition, when myinvention is in- Although I have shown and described only a singleembodiment of my invention, numerous modifications will be apparent tothoseskilled in the art. My invention, therefore, is not to be prior artor by the spirit of the appended claims.

I claim as my invention: p

1. In a wave-transmission system, a plurality of thermionic devices,means for supplying platepotential thereto, means for supplyinggrid-bias.- ing potential to said devices, and means individual to eachdevice for disconnecting the plate-potential supply therefrom uponfailure of the gridbiasing potentialsupply.

2. In a wave-transmission system, a plurality of thermionic devices,means forsupplying platepotential thereto, common means for supplyingall of said devices with grid-biasing potential, and means-individual tocertain of said devices for preventing the application ofplate-potential thereto in the absence of grid-biasing potential.

3. In combination, a plurality of thermionic amplifiers, a thermionicoscillation generator coupled thereto, means for supplying all of saiddevices with plate potential, means for supplying said devices withgrid-biasing potential, and means whereby a failure of grid-biasingpotential supply to said oscillation generator causes an in terruptionto the plate potential supplied to said amplifiers.

4. In combination, a plurality of thermionic amplifiers, a thermionicoscillation generator coupled thereto, means for supplying all of saiddevices with plate potential, means for supplying said devices withgrid-biasing potential, and 110 means whereby a failure of grid-biasingpotential V supply to said oscillation generator causes an interruptionto the plate potential supplied to all of said thermionic devices.

5. In a wave-transmission system, a thermionic oscillation generator, athermionic amplifier coupled thereto, means for providing platepotential for said devices, and means responsive to electricalconditions in the output circuit of said oscillation generator forcontrolling the application of plate potential to said thermionicamplifier.

6. In a wave-transmission system comprising at least two thermionicdevices connected in cascade, means for providing plate potential forsaid rentto flow in said grid leak, a plate-potential source, andmeansresponsive to said grid-leak current 'for controlling the connection ofsaid source in said output circuit.

ROBERT L. DAVIS.

